Thermosetting adhesives containing any of benzocyclobutene (BCB), novolac epoxy resins, and epoxy-containing polyorganosilsesquioxanes are known as adhesives for use in stacking of semiconductors and bonding of electronic components (Patent Literature (PTL) 1).
Disadvantageously, however, the thermosetting adhesives containing BCB require heating at high temperatures for curing, and exposure to such high temperatures may damage the adherends. Also disadvantageously, the thermosetting adhesives containing novolac epoxy resins, when subjected to high-temperature processes (for example, at 260° C. to 280° C.) such as lead-free solder reflow processes, are decomposed to outgas to thereby deteriorate in adhesion.
In contrast, the thermosetting adhesives containing epoxy-containing polyorganosilsesquioxanes can be cured at lower temperatures as compared with the thermosetting adhesives containing BCB, can form cured products having excellent adhesiveness (bonding properties) and adhesion to a substrate, and can maintain adhesiveness even when subjected to high-temperature processes. Disadvantageously, however, cured products of the thermosetting adhesives containing epoxy-containing polyorganosilsesquioxanes are susceptible to cracking caused by the application of cold thermal shocks.